Electric cable



no Model.)

A. E. DOLBEAR.

ELECTRIC CABLE.

Patented Nov. 15, 1887.

Irv/Iranian Wimp/5 w.

' UNITED STATES PATENT OFFICE.

AMOS EMERSON DOLBEAR, OF SOMERVILLE, ASSIGNOR OF ONEHALF TO FRANCIS M. HOLMES, OF BOSTON, MASSAOHUSETTS' ELECTRIC CABLE.

SPECIFICATION forming part of Letters Patent No. 373,394, dated November 15, 1887.

Application filed July 19, 1882. Serial No. 67,146. (No model.) Patented in England March 21, 1882, No. 1,368j

' sex and State of Massachusetts, have invented an Improvement in Electric Cables. (for which I have obtained a Patent in Great Britain, No.

' 1,368, hearing date March 21, 1882,) of which the following is a specification, reference being had to the accompanying drawings, in which- Figure 1 is a cross section of my cable on line or w of Fig. 2,- which is a central longitudinal section of the same. Fig. 3 is a diagram for illustration.

My invention is an electric cable which is made up of a flexible armored sheath and a conductor so secured within it that there is an air-space between the outer surface of the conductor aud'the inner surface of the sheath.

The compound sheath which forms part of my cable is made up of an inner tube of flexible material, a cushion incasing the tube, and an armor incas ing the cushion, and the best way now known to me of making this compound tube is that shown in the drawings, wherethcinnertubeis marked d,and is made up of paper rendered water-proofin various ways too well known to require description. This tube dis incased in gutta-percha,f, and the tube formed by the gutta-percha covering is wound with tarred twine g, and the whole is incased in the armor h, consisting of a numof the tube d depends in every case upon the diameter of the conductor a, which it isdesigned to contain,and is always enough greater than the external diameter of the conductora to afford an air-space between the outer sur- 5 face of the conductor and the inner surface of tube (2. This air-space is essential to my invention, the object of which is to produce a flexible armored cable with its conduct-or lying in but not filling its hollow core.

While the best form of cable would be that shown in Fig. 3, where there is no contact at all between the conductor and its sheath, it is practically impossible to construct cables in this way, and I consequently separate my conductor a for the inner surface of tube d by means of the spiral cord b, which is a very excellent bearing for the conductor, although it is not the only one which can be used in practice, as will be plain without further description.

I am aware of United States Patents No. 242,658, to Lamb, No. 249,008, to Codding, No. 258,029, to French, and English Letters Patent No. 2,326 of 1858, and No. 3,099 of 1876, and disclaim all that is shown in them, my cable differing radically from the things shown in these patents in that it is a flexible armored cable with a hollow core in which is a conductor which does not fill the core, space being left between the outer surface of the conductor and the inner surface of the core. Y

\Vhat I claim is- The improved electric cable herein described, made up of a sheath which is both armored and flexible, and a conductor between whose outer'surface and the inner surface of the sheath is a space, substantially as and for the purpose set forth.

AMOS EMERSON DOLBEAR.

Witnesses:

G. B. MAYNADIER, J. R. SNow. 

